The present invention relates to a highly-rigid composite material and a process for its manufacture. More particularly, the present invention relates to a composite material having a high Young's modulus and a process for its manufacture. The rigid composite material of the present invention may be employed for use in manufacturing automotive Vehicles and industrial robots, for example.
Recently, there has been a strong demand in the automotive industry for new materials which are light-weight for achieving low fuel consumption and have high damping characteristics for achieving a high level of comfort during driving.
Namely, when a highly rigid material is used for lightening an automotive part, such a part Can be small-sized, since its high rigidity enables it to absorb strains, i.e., it can resist bending or other forces. Furthermore, when a highly rigid material is used as a damping material, a small volume of the material can be used to absorb vibrations or strains.
A material having a high Young's modulus therefore has a remarkable potential for wide application in automotive parts and in many other structural members.
In order to increase rigidity, i.e., the Young's modulus of a material, it has been conventional to incorporate an alloying element or particles having a high Young's modulus in the material. However, when a solid-solution element (Re-element) is added to an Fe-based alloy, the Young's modulus is increased to about 21,000 to 22,000 kgf/mm.sup.2 at highest. When Nb(C,N) particles are added to an Fe-based alloy, the Young's modulus is about 24,000 to 25,000 kgf/mm.sup.2 at highest, and ductility and toughness are not satisfactory.
On the other hand, in the case of steel, it is conventional to apply thermomechanical treatment to the steel to orient or dispose crystals in a direction at which they exhibit a higher Young's modulus so that a high degree of rigidity can be obtained. According to this material design process, {111} planes are oriented in a given direction in the case of ferritic steel which has a body-centered cubic lattice. However, in the past as shown in Japanese Laid-Open Patent Application No. 23223/1981 and No.83721/1984, even if orientation of crystals in a given direction is performed by applying working with a working ratio higher than 5-10% and then heat treatment such as tempering or coiling at a temperature lower than 720.degree.-900.degree. C., the resulting Young's modulus is 23,000-24,000 kgf/mm.sup.2 at highest.